Anticorrosive



Patented Apr. 9 1946 ANTICORROSIVE Ernest W. Zublin, Sausalito, Ellis R.White, Albany, and Emmett R. Barnum, Berkeley, Calif., asslgnors toShell Development Company, San Francisco, Calil., a corporation oiDelaware No Drawing. Application February 8, 1943, Serial No. 475,198

19 Claims. (01. 252-56) The present invention relates to compositionshaving anti-corrosive, and especially rust-protective, properties, andmore particularly deals with compositions comprising a substantiallyneutral vehicle, such as normallyliquid or normally solid hydrocarbons,alcohols, esters (e. g., fatty oils and natural waxes), water, etc.,containing finely dispersed small amounts of certain free dicarboxylicacids in which the acid radicals are linked through one or more elementsselected from the group consisting of sulfur, selenium and tellurium.

Metallic surfaces, particularly those containing iron, requireprotection against the hazard of corrosion in the presence of water. Toillustrate: Moisture readily attacks finished or semi-finished metalobjects unless the metal surface is covered during storage or shipmentby a protective coating such as a slushing oil; water in Diesel enginefuels often corrodes closely fitted parts such as are found in Dieselengine unit type injectors; water in turbines corrodes turbine lubricantcirculatory systems, particularly the governor mechanisms of steamturbines; and water in hydrocarbon oils, such as gasoline, rusts steelstorage tanks and drums; water in anti-freeze compositions causescorrosion in automobile radiators, etc. Corrosion not only has adeleterious effect upon the metal surfaces, but also frequently loosensfinely divided metal oxides which may act as oxidation catalystsincreasing the rate of detericration of various organic compounds withwhich they come in contact or may enter between moving parts ofmachinery where they act as abrasives.

It is a purpose of this invention to produce potent corrosion-protectivecompositions of wide applicability. Another purpose is to produceslushing compositions of improved corrosion protective properties. Aspecific purpose is to produce rust-protective hydrocarbon composi-.tions, i. e., including various Diesel oils, steam turbine oils,greases, etc. Still another purpose is to provide anti-freezecompositions free from a tendency to cause rusting. Further, it is apurpose to produce a non-oily composition which can be used forrust-protection of ferrous metals and in general for protecting variousmetals against corrosion.

We have discovered that dicarboxylic acids having at least 16 carbonatoms in which the acid radicals are linked through a divalent sulfur,selenium or tellurium atom are such potent corrosion inhibitors thatthey are capable of effectively preventing rusting of ferrous metals andcorrosion in general, affording protection not only and generalcorrosion prevention, small amounts of these acids are finely dispersed(as in true or colloidal solution) in a suitable vehicle. Inasmuch asmany of them are quite soluble in many solvents, true solutionscontaining the necessary amounts can easily be prepared for mostpurposes.

The general formula of these acids is:

204-0 OOH (X wherein X is sulfur, selenium or tellurium, and u, v and ware integers, preferably 1 or 2. The unoccupied valences are tied to thesame or different hydrogen or hydrocarbon radicals, the latter of whichmay be aliphatic, cycloaliphatic, aromatic or mixed and may containsubstitution radicals which are not too strongly polar, such as halogen,etc., but should preferably be free from strong polar radicals, such asThe above formula may take the following form:

As indicated before, the acid should'have a total number of carbon atomsnot less than 16, and preferably between about 20 and for goodanti-corrosive properties. Both true solutions and colloidal dispersonsin various vehicles are effective in the matter of corrosion protection.However, true solutions are preferred for two reasons: first, colloidalsolutions may under some circumstances coagulate, in which case at leasta portion of the active protective agent is eliminated; and second,colloids tend to cause emulsification of oily vehicles with water, whichin many instances, such as in the lubrication of steam turbines, isundesirable. It is, of course, desirable that the acids be relativelyresistant to oxidation, and therefore they should not contain more thanone aliphatic double bond per hydrocarbon radical and preferably none.

Generally, in the presence of copper. acids containing a link of asingle x atom (X being S, Se or Te) seem to impart to oils longerinduction periods than acids having X-X linkage, while the latter impartlower rates of oxygen absorption after the inductipn period. Thusdisulfide, diselenide or ditelluride acids may be preferred for someoils, while acids with mono linkages may be better for other oils. morethan two sulfur atoms may also be used. They are, however, believed tocontain only two sulfur atoms in the normal chain between the carboxylradicals, the remaining sulfur being attached in the form of a branch.such as s s I H --s-- s etc. If desired, the carboxyl radicals may belinked through a sulfone radical The closeness of the sulfur, seleniumor tellurium to the carbowl radical has some bearing on. thecorrosion-protective properties of the acids. In general, the closerthey are, the more potent the compound is, other things being equal.Thus, from this angle, acids in. which the sulfur, selenium or telluriumatoms are in alpha or beta position to at least one, and preferably bothcarboxyl radicals are the best anticorrosives.

Accordingly, among the groups of acids are several which areparticularly useful. For example, di-fatty acid alpha sulfides,selenides and tellurides having the formula Polysulfide linkages ofradicals, the latter preferably being aliphatic although they maycomprise cycloaliphatic or aromatic groups. The unoccupied valences aretied to hydrogen or hydrocarbon radicals, which groups. X again issulfur, selenium or tellurium; n is preferably 1 or 2; and o is 1 orpreferably 2. The total number of carbon atoms is preferably 20 or more.

The dicarboxylic acids of this invention may be produced in severalways. One convenient method comprises reacting a chlorinated fatty acidor other suitable monocarboxylic acid with an alkali metal sulfide orpolysulfide. Commercially available alkali metal sulfides are usuallymixtures containing mono-, diand sometimes higher polysulfides.Therefore this reaction may be utilized to produce mixtures of differentsulfide dicarboxylic acids. Such mixtures are very excellent for thepurpose of this invention, since they are usually more soluble invarious vehicles and as oxidation stable as the best of the pureindividual compounds.

Disulfides may be produced by first preparing a hydrosulfide derivativeof a fatty acid or other suitable carboxylic acid by reaction of achlorinated carboxylic acid with Nal-IS, KHS, etc.,

then oxidizing the hydrosulfide to the disulfide.

wherein o is l or 2, and R1 and Rs are alkyl mono-, diand higherpolysulfides; di-phenylstearic acid alpha sulfides; dicyclohexyl-stearicacid alpha sulfides, di-petroleum naphthenic acids alpha sulfides, etc.Obviously, the two fatty or naphthenic acids linked by the sulfur may bedifierent as, for example, in phenyl stearic acidacetic acid sulfides.

Groups of acids somewhat different from the above are represented by theformulae:

COR

Cmwi V (20011 coon wherein Rr-Ra are hydrogen or hydrocarbon alphasulfides including both.

' Higher polysulfides may be obtained by oxidizing with sulfur in thepresence of lead oxide.

Asymmetric dicarboxylic acids may be produced, for example, by reactinga suitable chlorinated monocarboxylic acid with an alkali metal salt ofthioglycolic acid or of a fatty or other suitable monocarboxylic acidhydrosulfide.

Suitable monocarboxylic acids for the production of our dicarboxylicacids include fatty acids, such as acetic acid, propionic, butyric,isobutyric, valeric, caproic, caprylic, decylic, undecylic, lauric,myristic, palmitic, stearic, arachic, behenic, oleic, phenyl acetic,phenyl propionic, phenyl stearic, tolyl stearic, naphthyl acetic,naphthol stearic, acids, etc. Naphthenic acids, such as are obtained bycaustic alkali extraction of relatively high-boiling straight-runpetroleum etc., may be used; or synthetic naphthenic acids,

such as cyclohexyl acetic, cyclohexyl propionic, cyclohexyl stearicacids, corresponding alkyl cyclohexyl, tetrallyl, dicyclohexyl fattyacids, or acids derived from naphthenes obtained by hydrogenation ofisophorone, diisophorone and homologues, etc. In choosing amonocarboxylic acid from the list for use in a certain reaction, sightmust not be lost of the fact that the dicarboxylic acid must have aminimum of 16 carbon atoms.

The vehicles to which dicarboxylic acids of this invention may be addedfor the purpose of producing corrosion-protective compositions may bedivided 'into several groups. In the first place, they may be liquids orplastics, the only requirements as to their physical state being (inaddition to their being able to act as carrier for the acids undernormal atmospheric conditions) that they be spreadable overmetal-surfaces. Spreading -maybe accomplished by immersing, flooding,

. spraying, brushing, trowelling, etc.

After being applied, all or part of the vehicle- Q may be evaporated, orit may be more or less permanent. In other words, both volatilecaraaeaaoa riers may be used, or substances which do not materiallyvolatilize under normal atmospheric conditions. As to chemicalrequirements, the vehicle must be stable under ordinary conditions ofstorage and use and be inert to the active inhibitors.

Thus the vehicle should preferably be substantially neutral, although itmay be weakly acidic or basic, preferably having dissociation constantsnot above about In vehicles of low dielectric constant, as hydrocarbonoils, which are not conducive to ionization of dissolved electrolytes,relatively small amounts, i. e., about .l%-5% of various carboxylicacids, such as fatty or naphthenic acids, may be present, and in manyinstances this may even be beneficial.

Both polar and non-polar vehicles may be employed. Among the former arewater, alcohols, such as methyl, ethyl, propyl, isopropyl. butyl, amyl,hexyl, cyclohexyl, heptyl, methyl cyclohexyl, octyl, decyl, lauryl,myristyl, cetyl, stearyl, benzyl, etc., alcohols; polyhydric alcohols asethylene glycol, propylene glycol, butylene glycol, glycerol, methylglycerol, etc.; phenol and various alkyl phenols; ketones as acetone,methyl ethyl ketone, diethyl ketone, methyl propyl, methyl butyl,dlpropyl ketones, cyclohexanone and higher ketones; keto alcohols asbenzoin, others as diethyl ether, diisopropyl ether, diethylene dioxide,beta-beta dichlor diethyl ether, diphenyl oxide, chlorinated cliphenyloxide, diethylene glycol, triethylene glycol, ethylene glycol monomethylether, corresponding ethyl, propyl, butyl ethers; neutral esters ofcarboxyiic and other acids as ethyl, propyl, butyl, amyl, phenyl, cresyland higher acetates, propionates, butyrates, lactates, laurates,myristates, palmitates, stearates, oleates, ricincleates, phthalates,phosphates, phosphites, thiophosphates, carbonates; natural waxes asCarnauba wax, candellila wax, Japan wax, jojoba oil, sperm oil; fats astallow, lard oil, olive oil, cottonseed oil, perilla oil, linseed oil,tung oil, soya bean oil, flaxseed oil, etc.; weak bases as pyridine,alkyl pyridines, quinolines, petroleum bases, etc.

Vehicles of little or no polarity comprise hydrocarbons or halogenatedhydrocarbons as liquid butanes, pentanes, hexanes, heptanes, octanes,benzene, toluene, xylenes, cumene, indene, hydrindene, alkylnaphthalenes; gasoline distillates, kerosene, gas oil, lubricating oils(which may be soap-thickened to form greases), petrolatum, parafiin wax,albino asphalt, carbon tetrachloride, ethylene dichloride, propylchloride, butyl chloride, chlor benzol, chlorinated parafiin wax, etc.

The amounts of the dicarboxylic acids which must be incorporated in theabove vehicles to produce corrosion-protective compositions varyconsiderably with the type of vehicle used. As a general rule,thepresence of resinous materials, particularly those of a colloidalnature, calls for relatively larger amounts of inhibitors. Resinousmaterials which interfere with the activity of the inhibitors compriseasphaltenes, petroleum resins, various other natural resins, as rosin,resins formed by polymerization of*drying fatty oils,phenol-formaldehyde resins, glyptal type resins formed by esterificationof polyhydric alcohols with polycarboxylic acids, etc.

In the absence of such resinous materials, amounts required of thedicarboxylic acids vary from about .00l% up to about .l%, althoughlarger amounts may be used. However, where the acids are in colloidaldispersion, rather than chlorinated kerosene,

in true solution, a concentration in excess of about .l% may result inrelatively quick loss of part or the inhibitor by precipitation andsettling.

In the presence of resins and other colloids,"

amounts in excess of .l% and up to 5% may be required. inasmuch asresins may act as protective colloids, compositions containing theselarge amounts of colloidally dispersed inhibitors, together with resin,may be quite resistant to precipitation and settling.

Since resinous and gummy substances in the Vehicles do call for greateramounts of inhibitors, it is usually desirable to refine normally liquidvehicles thoroughly and free them from gummy substances, therebyimparting to them maximum inhibitor susceptibility. This is ofparticular importance, for example, in lubricating oils, specificallysteam turbine oils, which are advantageously highly refined before theinhibitor is introduced. Suitable refining treatments include, forexample, extraction with selective solvent for aromatic hydrocarbons asliquid S02, phenol, furfural, nitrobenzene, aniline, betabeta-dichlorinediethyl ether, antimony trichloride, etc.; treatment with AlCls,sulfuric acid, clay, etc. If the treatment produces a sludge, specialcare must be taken to remove it very thoroughly and completely.

Applications of the various corrosion-protective compositions vary overa wide range. Hydrocarbon compositions are of special importance. Forexample, gasoline's stored in drums may cause rusting of the drumsbecause of the accumulation of water. This is particularly bad intropical countries where the moisture content of the air is high andwide variations in temperature over a 24-hour cycle cause considerablebreathing of the drums.

Diesel fuels may cause corrosion of injection nozzles.

Lubricating oils and greases made of lubricating oils and soaps normallyallow corrosion or even may cause corrosion of various metal parts withwhich they come in contact, such as bearings, crank-cases, shafts, etc.This problem arises in many types of engines and is often particularlyserious in steam turbines. The presence of the inhibitors of thisinvention will afford excellent protection in all of the aboveinstances.

Rusting of ferrous metals exposed to the atmosphere during usage orstorage is a serious problem. This is of particular importance whereaccurately machined parts must be preserved. Slushing oilscomprisingvarious types of liquid or plastic hydrocarbons, fats, waxes, lanolin,are employed to protect the metals against this attack, and theinhibitors of this invention have great value as an active component insuch slushing oils. I

Cutting oils, EP lubricants, due to their content of sulfur and/orchlorine in various active forms, frequently are quite corrosive. Thedicarboxylic acids efiectively inhibit this corrosion.

Among the non-hydrocarbon compositions which frequently cause corrosiondifiiculties, antifreezes used in automobile radiators and the like maybe mentioned. The dicarboxylic acids effectively eliminate theircorrosiveness. Antifreezes usually comprise or consist of water-misciblealcohols, such as methanol, ethanol, isopropanol, glycol, glycerol, etc.

So-called hydraulic oils, damping oils, etc. which frequently are basedon non-hydrocarbon liquids, such as various alcohols, esters, etc., havein the past introduced some corrosion difliculties which can effectivelybe prevented of this invention.

Dispersions of the dicarboxylic (ll-fatty acids in water may be usefulin the rust-proofing of by the acids We claim as our invention:

1. A corrosion-preventive composition comprising predominantly anoleaginous vehicle containing finely dispersed a small corrosioninhibitmetals which after treatment must not be greasy ing amount of adicarboxylic acid having at least as, for example, various machine partsin the 16 carbon atoms, the two acid radicals in said textileindustries, particularly in the knitting of acid being linked through anelement selected fine dry goods. If desired, solutions or disperfrom thegroup consisting of S, Se, and Te, said sions in low-boiling alcohols,etc., may be used element being attached to a carbon atom not for thesame purpose. it) further removed from the carboxyl radical than It isunderstood that the corrosion-protective the beta position. compositionsof this invention may contain other 2. The composition of claim 1wherein the ingredients in addition to the vehicle and the number ofcarbon atoms in said acid is between dicarboxylic acids, However, suchadditional innd 60.- gredients must be chemically inert to the acid 16 hComposition of aim 1 e ein sa and the vehicle employed. Thus strongoxidizing acid i in c l l al solution. agents as chlorine, peroxides,etc., must be avoid- A cormsiompr-evenfive compositlon ed as they tendto destroy the inhibitors. Strong lmsing predominantly n oleasinousvehicle 9 bases, particularly in ionizing vehicles, as m talning finelydispersed a small corrosion inhibitwater, alcohols, etc., willneutralize the diacids 20 s amount of dicarboxylic id having at leastand thereby render them relatively ineffective. 15 carbon awms am1having the formula Likewise, strong acids may reduce their eifecwtiveness. However, in non-ionizing solvents, i. e., P0003 in hydrocarboncompositions, chlorinated hydrox v carbons, etc., the presence ofrelatively small a quantities of primary, secondary and tertiary Knitrogen bases and/or carboxync acids Wm wherein X is an elementselected from the roup normally interfere with the activity of theinhibconslstm g of S, Se and Te, 14 and v are each initor. On the otherhand, even in these vehicles 3o tegers of less than three, and w isequal to one. very strong bases as various onium bases, or very t id Ifi 01 d should not be 5. A corrosion-preventive composition coms ac S ason c a prising predominantly an oleaginous vehicle confs d1 1 h d be m ath tainin a small corrosion inhibiting amount of a ng n compos ons an edicarboxylic acid having at least 20 carbon atoms like may containvarious types of omdation inand the i0 1 5 Imu a hibitors as alkylatedphenols, aromatic amines, C 0 preferably secondary amines, aminophenols; as H C OH well as various EP compounds containing halo- )0 gen,S, P, As, etc., anti-wear compounds, de- MAE-{F0005 tergents,sludge-preventing compounds, pour point reducers, thlckeners such assoaps, etc. z i R2 are z f a g hycglocmbon Likewise, fats, anti-freezes,etc., may contain m P s an elemen Se ec 8 mm 9 group antboxidants.consisting of S, Se, and Te, and o is 1 or 2.

Examples 6. A corrosion-preventive composition comprising predominantlya substantially neutral The effectiveness of several dicarb yli acidsoleaginous vehicle containing finely dispersed a of this invention insuppressing corrosion was desmall corrosion inhibiting amount of adicarboxtermined,by a test which consists of subjecting ylic acid havingat least 20 carbon atoms, the two a polished steel strip to the actionof a vigorously carboxylic acid radicals in said acid being linkedstirred emulsion of a turbo ramnate of 150 S. U. through a singledivalent sulfur atom in alpha viscosity at 100 F. with 10% by volume ofwater position with respect to each of said carboxylic at 167 F. In somecases, distilled water was acid radicals. used, in others a 2% solutionof NaCl, or sea '7. A corrosion-preventive composition comwater from thePacific Ocean, or a synthetic sea prising predominantly an oleaginousvehicle conwater which had the same analysis as real sea taining finelydispersed a small corrosion inhibitwater, When using distilled waterprotection was ing amount of di-stearic acid alpha, alpha monoperfect inall cases for more than 48 hours. Brine sulfide. waters gave thefollowing results: 8. A corrosion-preventive composition com- Additive 1Water Time Corrosion Hours .0191, alpha alpha dilauric acid sulfide 2%NaOl 48 None-perlcct protection.

Synthetic sea water. 48 Do.

.0l% alpha alpha dimyristic acid sulfide 2% NaCl 24 None-perfectprotection.

Seawater 25 Perfect. Synthetic sea water. 48 Do.

.Ol% alpha alpha dipalmitic acid sulfide Synthetic sea water... 48Perfect.

.0l% alpha alpha distearic acid sulfide 2% NaCl 48 Perfect.

Do Sea water 44 Slight corrosion, less than 10%. Do Synthetic seawater... 48 Noneperfect protection. .005% alpha alpha distearic acidsulfide .do 25 Slight corrosion, less than 10%.

.Ol% alpha-lauric alpha-stearic acid sulfide Synthetic sea water 48Noneperlect protection.

.0l% alpha alpha distearic acid dlsulfide 2% N aCl 48 Perfect.

. Synthetic sea water... 24 Very slight corrosion.

.0l% alpha hexadecyl thicglyoolic'acid 2% NaCl 24 Very slight corrosion.

prising predominantly an oleaginous vehicle containing finely disperseda small corrosion inhibitingamount of di-myristic acid alpha. alphamono-sulfide.

9. A corrosion-preventive composition comprising predominantly anoleaginous vehicle con-- taining finely dispersed a small corrosioninhibiting amount of di-palmitic acid alpha, alpha mono-sulfide.

10. A corrosion-preventive composition comprising predominantly asubstantially neutral oleaginous substance containing a small corrosioninhibiting amount of-a free dicarboxylic acid having at least 16 carbonatoms, the two acid radicals in said acid being linked through anelement selected from the group consisting of S. Se or Te, said elementbeing attached to a carbon atom not further removed from the carboxylradical than the beta position.

11. The composition of claim in which said substance is normally liquid.

12. The composition of claim 10 in which said substance is normallyplastic.

13. A corrosion-preventive composition comprising predominantly asubstantially neutral oleaginous substance free from resins containingfinely dispersed .001%-.1% of a free dicarboxylic acid having at least16 carbon atoms, the two acid radicals in said acid being linked throughan element selected from the group consisting of S, Se or Te, saidelement being attached to a carbon atom not further removed from thecarbonyl radical than the beta position.

14. A corrosion-preventive composition comprising predominantly asubstantially neutral oleaglnous substance containing resins-and finelydispersed .l%-5% of a free dicarboxylic acid having at least 16 carbonatoms, the two acid radicals in said acid being linked through anelement selected from the group consisting of S, Se or Te, said elementbeing attached to a carbon atom not further removed from the carboxylradical than the beta position.

15. A corrosion-preventive lubricating oil containing finely dispersed.001%-1% of a free dicarboxylic acid having at least 16 carbon atoms.the two acid radicals in said acid being linked through an elementselected from the group consisting of S, Se or Te. said element beingattached to a carbon atom not further removed from the carboxyl radicalthan the beta position.

16. A corrosion-preventive composition comprising predominantly acarboxylic acid ester containing finely dispersed a small corrosioninhibiting amount of a tree dicarboxylic acid having at least 16 carbonatoms, the two acid radicals in said acid being linked through anelement selected from the group consisting of S, Se or Te, said elementbeing attached to a carbon atom not further removed from the carboxylradical than the beta position.

17. A corrosion-preventive composition comprising predominantly a fat,and finely dispersed therein a small corrosion inhibiting amount of afree dicarboxylic acid having at least 16 carbon atoms, the two acidradicals in said acid being linked through an element selected from thegroup consisting of S. Se or Te, said element being attached to a carbonatom not further removed from the carboxyl radical than the betaposition.

18. A noncorrosive anti-freeze composition comprising predominantly awater-soluble alcohol and finely dispersed therein a small corrosioninhibiting amount of a free dicarboxylic acid having at least 16 carbonatoms, the two acid radicals in said acid being linked through anelement selected from the group consisting of S, Se or Te, said elementbeing attached to a carbon atom not further removed from the carboxylradical than the beta position.

19. A corrosion-preventive composition comprising predominantly anoleaginous vehicle containing finely dispersed a corrosion-inhibitingamount of a di-fatty acid having at least 20 carbon atoms, the two acidradicals in said acid being linked through a single divalent sulfur atombetween two carbon atoms not further removed from each of the acidradicals than the beta position.

ERNEST W. ZUBLIN. ELLIS R. WHITE. EMME'II R. BARNUM.

